Here are some bits 'o Crinoid that I've found at Arkona. I've not yet found an complete Crinoid or even a whole Calyx but there is plenty of evidence to be found.
This is a plate from the bottom of a Calyx of a Megistocrinus Crinoid. The Heavy lined side faced out with the stem attaching in the middle of the circular shaped area. The flip side of the piece is smooth (because this would have been inside the Calyx) and shows a star where the stem connected to the rest of the animals tissue. I found this in float from the Hungry Hollow member of the Widder Formation.
These two plates have the arms of an Arthroacantha crinoid on them. These have been preserved on top of a piece of "crinoid lens" that was found in the Arkona formation.
These lenses can be used as an indicator of a rich layer of intact, articulated crinoids just above them in the strata. Sadly all I found were the left over pieces from a recent scraping of the Arkona formation for clay. Note the presence of Platycerid gastropods on both pieces. The snails lived a corprophageous (fed on the waste from the Crinoid) lifestyle by planting themselves over the anal tube on top of the Arthroacantha crinoids.
Speaking of Arthroacantha's, below is the bottom set of plates from a Calyx. Note the triangle shaped attachment point for the stem and the small pore like dimples on the side. In life the dimples would have had small spines sticking out. This was found in float from the Hungry Hollow member of the Widder foramtion.
Here we have two holdfasts on top of a piece of Platyaxum frondosa coral. They could be from Crinoids but also from Bryozoans as it is hard to tell sometimes. From the Hungry Hollow member of the Widder Formation
Lastly we have a section from a Crinoid stem with parts of "wings" on the side. I've been told by Joe K. that the stem sections come from a Megistocrinus crinoid. I can't find any intact examples on the web to see what the wings would have looked like in life position unfortunately.
These stem sections are extremely common in the Hungry Hollow member of the Widder formation.